1. Field of the Invention
The present invention relates to a molding metal mold, and more particularly, to a molding metal mold capable of improving the precision of the shape of the molded item.
2. Description of the Related Art
In general, in production of molded items having the same shape, methods are used such as pouring into a molding metal mold a material such as melted resin, and pressing a material in the molding metal mold. The molding metal mold is provided inside with a cavity having concavities and convexities reversed to those of the molded items to reflect the shape thereof. To pour the material into the cavity, the molding metal mold is separated into two or more portions at a parting surface passing through the cavity.
Although the separate metal molds each have a positioning structure for positioning with a counterpart mold, when the positioning is conducted simply by fitting a pin into a hole, it is necessary to clearance-fit the pin to the hole to smoothly close and open the mold. This clearance causes a disparity between the cavity surfaces of one and the other molds, resulting in an error in the shape of the molded items.
To counter this problem, a technique is proposed to accurately align the separated molds by fitting convex and concave tapers to eliminate the clearance, instead of by a positioning with simple use of a pin and a hole, as disclosed in Kokai (Japanese Unexamined Patent Publication) No. 2002-225086, for example.
To fit the convex and concave tapers to each other, a technique is employed to abut the both taper surfaces to each other to perform positioning in the two-dimensional direction along the surface perpendicular to the axis of the tapers. However, because the convex and concave tapers themselves have errors in dimension and shape, in order to make the taper surfaces to surely abut, there needs to be a clearance between the top surface of the convex taper (a flat surface on the top of the taper) and the bottom surface of the concave taper.
However, the clearance causes an error in thickness and burrs to the molded items. Therefore, in the positioning of the molding metal mold, it was prioritized to ensure that the top surface of the convex taper and the bottom surface of the concave taper abut to each other, to provide a design in which a clearance exists between the taper surfaces. However, the clearance led to a further problem of causing a positioning error.
In light of such a background, the present invention aims to provide a molding metal mold capable of producing a molded item having a highly precise shape by accurately positioning the separate metal molds.